Shopify Plus - only allow certain B2B customers access to certain ship methods

Hi,

I’m working on a Shopify Plus site for a client who needs to carefully manage shipping methods based on 2 factors:

Customer login
Total items in the order

They need certain shipping methods to only be available to specific customers. They work with a number of freight-forwarding companies, and certain freight-forwarders are only available to specific customers.

They also offer FedEx shipping, but only on “smaller” orders, so once a cart exceeds a specified number of items, we would like to disable FedEx as an option and only allow the freight-forwarder assigned to that customer as the only ship options.

Hopefully, what I’ve described makes sense. Is this something Shopify Plus can easily support, and any tips on how to get started?

thanks!